https://bugs.gentoo.org/911333
https://github.com/cython/cython/pull/5572
https://github.com/cython/cython/commit/ca69b359b040bf6c0fc90692bbea3bdd9d7877e6

From ca69b359b040bf6c0fc90692bbea3bdd9d7877e6 Mon Sep 17 00:00:00 2001
From: Eli Schwartz <eschwartz@archlinux.org>
Date: Fri, 28 Jul 2023 06:52:03 -0400
Subject: [PATCH] Only write the version to stderr, if it's a separate file
 descriptor from stdout (GH-5572)

At least one project tries to detect the Cython version by redirecting stderr to
stdout and capturing it. This is done in pure POSIX shell, so it probably seemed
like the simple and obvious solution for a less capable programming language
given that no output at all was expected on stdout.

But the result is that the version number appears twice, and then gets misparsed
and ends up triggering bad assumptions in the code running cython.

It turns out that it's pretty easy to just print once, though. Detect when
stdout and stderr are redirected to the same location, and only print once.

See https://github.com/cython/cython/issues/5504
Fixes https://bugs.gentoo.org/911333
--- a/Cython/Compiler/Main.py
+++ b/Cython/Compiler/Main.py
@@ -776,7 +776,7 @@ def main(command_line = 0):
         print("Cython version %s" % __version__)
         # For legacy reasons, we also write the version to stderr.
         # New tools should expect it in stdout, but existing ones still pipe from stderr.
-        if not sys.stderr.isatty():
+        if not sys.stderr.isatty() and os.fstat(1) != os.fstat(2):
             sys.stderr.write("Cython version %s\n" % __version__)
     if options.working_path!="":
         os.chdir(options.working_path)